Variable volume pump and hydraulic transmission



Feb, 12, 1935. J 5 PIGQTT 1,990,750

VARIABLE VOLUME PUMP AND HYDRAULIC TRANSMISSION Filed March 2, 1931 6Sheets-Sheet 1 Feb. 12, 1935. I js PIGQTT v 1,990,750

. VARIABLE VOLUME PUMP AND HYDRAULIC TRANSMISSION Feb. 12, 1 935. J 5PIGOTT 1,990,750

I VARIABLE VOLUME PUMP AND HYDRAULIC TRANSMISSION Filed March 2, 1931 sShets-Sheet 5 gwtwntoz Fb; 12 1935. R. J. s. PIGOTT 1,990,750

VARIABLE VOLUME- PUMP AND HYDRAULI C TRAN SMI S S I ON Filed March 2,1931 -6 Sheets-Sheet 4 Feb. 12, 1935. R s plGOTT l990,750

VARIABLE VOLUME PUMP 'AND HYDRAULIC TRANSMISSION Filed March 2, 1951 sSheets-Shae 5 Feb. 12, 1935, R. J. 5. QG TT VARIABLE VOLUME PUMP ANDHYDRAULIC TRANSMISSION Filed March 2, 19:51 a Sheets-Sheei a PatentedFeb. 12, 1935 VARIABLE VOLUME PUMP AND HYDRAULIC TRANSMISSION Reginald'J. S. Pigott, Pittsburgh, Pa., assignor,

by mesne assignments, to Gulf Development Corporation, corporation ofDelaware Research & Pittsburgh, Pa., a

Application March 2, 1931, Serial No; 519,571 27 Claims. (Cl. 103 -126)My invention relates to pumps for general use and applicable tohydraulic transmission systems.

The present invention includes improvements in the pumping mechanismshown in my prior Patent 1,742,215 of January 7, 1930 and has for anobject the provision of a pump adapted to give a greater capacity perunit of occupied space.

' Another object of-the present invention is to materially increase thetime for suction and discharge at any given rotational speed of thepump, thereby permitting the use of relatively low velocities of flow inthe pump and thus reducing hydraulic shock losses.

A further object resides in the provision of' a pump having longercapillary passages and more teeth in contact at any one time thanheretofore whereby leakage is considerably reduced.

A further object resides in the provision of a pump of the characterreferred to wherein the flow of fluid to the pump is substantially inthe same direction as the rotation of the pump rotors whereby the fluidenters and leaves the rotors with practically no shock losses.

An additional object is to provide a pump which readily lends itself tomanufacture, being simple and rugged in construction and comprising buta relatively few parts each of which may be economically machined.

Another object is to provide a variable volume pump including gearsconstituting the pumping elements and adapted to be moved more or less"into and out of mesh or engagement whereby to increase or decrease thecapacity of the pump, simple and inexpensive means being provided toseal or cut off the portions of the gearsat any time out of mesh.

A further object is to provide a pump including a rotary shaft havingbearings and packing, and means for increasing the flow of oil throughthe bearings of the pump shaft and at the same time relieving thepressure of the oil on the shaft packing.

Another object is to provide a pump which will be free of trapping andthe noise and damage resulting therefrom.

Other objects and advantages of my present invention will appear fromthe more detailed description thereof.

The rotor combination or pumping elements of; my present inventionconsist of a pinion within an internal or ring gear, the latter havingone tooth more than the former. .As herein hydraulic shock losses.

ing' drawings illustrating a preferred construcdisclosed the pinion isprovided with eight teeth and the ring gear with nine. However, it is tobe understood that the number of teeth on the pinion and ring gearpermits of considerable variation. 5

An advantageous feature of the internal-external gear combination of onetooth difference,

is that this combination yields the maximum volume displacement perrevolution for a given sized pinion and the suction and discharge 1operiods are each theoretically one-half revolution or 180 degrees. Inall other teeth combinations, the suction and discharge periods are lessthan 180 degrees each, the teeth do not touch for a portion of therevolution, and a 'crescentr shaped filler is required to effectsealing. In the present construction the time for suction and dischargeat any given rotational speed is very greatly increased over that ofother designs. This permits the use of relatively low velocities of flowin the pump thereby reducing For a more detailed understanding of myinvention, reference will be'had to the accompany- 25 tion adapted foruse in the pumping of liquid and which will be described as applied tothe pumping of oil. However, the invention is not to be construed aslimited to 'the particular construction and use chosen for illustrationbut 30 that various changes and modifications may be made thereinwithout departing from the spirit.

and scope of the invention as defined in the appended claims.

In the drawings:

Fig. 1 is a longitudinal sectional view of the variable volume pump insubstantially full volume position, but with the gear and pinion aboutone-sixteenth inch out of mesh;

Fig. 2 is a sectional view on the line 2-2 of Fig. 1;

Figs. Sand 4 are sectional views taken on the lines 3-3 and 4-4 ofFigure 1 respectively;

Fig. 5 is a sectional view of the follower member taken on the line 5-5of Figure .2;

Fig. 6 is a section on the line 6-6 of Figure 5;

Fig. 7 is a perspective view partly in section and showing the pinionand ring gears partially disengaged and in approximately the half-volumeposition;

Fig. 8 "is a plan view of the variable volume pump as shown in Figures 1to 7;

Fig. 9 is a vertical longitudinal section of a constant volume motor orpump; and

Fig. 10 is a transverse sectional view on the line 10-10 of Figure 9.

Referring more particularly to the drawings and to the variable volumepump of Figs. 1 to 8, at 1 is shown the pump casing provided at itsupper portion with a suction inlet 2 and a discharge outlet 3 for theintroduction and discharge respectively of the oil or other fluid beingpumped. The ends of the casing are closed by means of a front head 4having spud 5 and rear head 6 having spud '7 the latter spud being thelarger in diameter and disposed eccentrically with respect to the spud5. Disposed within the casing and adapted for rotation therein is aninternal or ring gear 8 having teeth 9 and tooth spaces 10, the gearforming with the casing' 1 and a follower hereinafter described, thesuction passage 11 and a discharge passage 12 communicating respectivelywith inlet 2 and outlet 3. The interior of the ring gear communicateswith the suction and discharge passages by means ofcircumferentially'spaced ports 13 disposed between the teeth of thegear. A pinion 14 having teeth 15 is disposed within and adapted forengagement with gear 8 and is fixed by means of key 18 to shaft 17iwhich is driven from any suitable prime mover or source of power in thedirection indicated by the arrow in Figure 2. A packing gland 18 andpacking nut 19 are provided for shaft 17 while at 20 and 21 respectivelyare shown roller and thrust bearings for'the pinion.

The pinion is made with one tooth less than the ring gear which ismounted eccentric to the pinion by about one-half the tooth depth sothat, as best shown in Figure 2, the teeth of the gear are fully engagedat the top, and just clear. the tips of the pinion teeth at the bottom.In the particular modification of the invention illustrated in thedrawings, the pinion and gear are provided with eight and nine teethrespectively but the exact number is not important as long as the gearhas one more tooth than the pinion. The arrangement is such that thegear and pinion mesh deeply overa considerable are at the top. At thebottom of the device, the tips of the gear and pinion teeth contact ormaintain small clearance continuously for a space of about two andone-half gear teeth so that sometimes three and at other times two teethare simultaneously in contact or at close clearance at the tips.

The front spud 5 extends inward to the side of thepinion 14 and isconcentric with gear 8 to fit snugly inside the top of gear teeth 9 whenthe gear is moved to the left (Fig. 1) or in the direction of head 4.The rear spud 7 likewise extends inward to the side of the pinion and isof the same outside diameter as the pinion and concentric therewith.

Mounted for sliding movement within the easing is an annular followermember 22, the intermediate side portions of which, as best shown inFigure 5, are cut out to form with the casing and gear 8 the suctionpassage 11, communicating with inlet 2, and discharge passage 12,communicating with outlet 3, thereby leaving an upper abutment 23 and alower abutment 24. The rearward end of follower member 22 (Figs. 1 and7) is bored to fit snugly over spud 7 and is adapted for slidingmovement thereon. The distance from the cut out portion or surface ofthe follower to the rear edge thereof opposite head 6 is equal to thelength of spud 7 and the right hand side (Fig. 1) of ring gear 8 abutsagainst surface 25 of the follower. When gear 8 and pinion 14 are infull mesh, the follower member is all the way over to the rear end ofthe casing and against head 6.

The forward end of follower 22 is bored to receive gear 8 for rotationwithin the abutments 23 and 24 and against vertical surface 25 andhorizontal surface 25' and is closed by an annular follower plate 26held within the forward end of the follower member by a retaining ring27, the follower plate 26 fitting snugly over and slidable on spud 5 andforming the front wall of the pumping chamber enclosing the gear andpinion. The follower member and plate form a front balancing chamber 28with head 4 and when the follower is moved forward, a rear chamber 29 isformed between the head 6 and the rearward end of the follower. Afeather or key 22' is provided between the casing and the followermember for preventing rotation of the follower within the casing and onwhich the follower slides longitudinally.

From the structure Just described, it will be seen that, ring gear 8fitting snugly within the follower member and plate and pinion 14 beingfixed to rotary shaft 17, movement of the follower member frontwisetoward head 4 will slide the gear partially out of engagement with thepinion, depending upon the extent of sliding movement of the follower,while movement of the follower member rearward toward head 6 will bringthe gear back into full mesh with the pinion. Abutments 23 and 24, inwhich gear 8 rotates, form a seal between suction passage 11 anddischarge passage 12 at the top and bottom of the casing respectivelywhile further scaling is effected between the suction and dischargepassages by contact of the ring gear with the surfaces of the upper andlower abutments in which it rotates, the abutment 24 extending over anare great enough to span a little more than one tooth space 10 plus twogear ports 13 and the abutment 23 extending over an area about half thatof abutment 24. A further seal is effected between the suction anddischarge passages by contact between the teeth of the pinion and ringgear which, as already explained, mesh for a considerable are at the topof the casing while the tips of the teeth contact adjacent the bottom ofthe casing. A further seal around the periphery of the gear is formed bysurface 25' in which the gear rotates, surface 25, and the inner face ofplate 26. The surfaces 25' of the follower form a bearing completelyaround the ring gear.

It will further be seen from the construction thus far described that,when the gear 8 and pinion 14 are partially disengaged, the rear facesof the pinion teeth 15 are bounded by spuds 7. The tops or crests of thepinion teeth 15 out of engagement with the gear 8 are bounded and sealedby the rearward cylindrical portion of the follower member which snuglyfits over the spud 7.

The toothed spaces of the pinion 14 are sealed from one anotherlongitudinally of the pinion axis by the rearward bore of the followermember 22 when the gear is moved longitudinally of the pinion or out ofengagement therewith. Also the front faces of the pinion teeth arepartly covered by the spud 5, and where not thus covered are incommunication over the spud 5 with the corresponding pockets ortoothspaces 10 between the ring gear teeth, and consequently the inner faceof the plate 26. Similarly the ring gear pockets 10 are bounded on thefront end of the follower plate 26 on the tips of the teeth by the spud5 and the pockets so formed are in communication at the rear end withthe engaged portion of the teeth and the pockets between the teeth ofthe pinion.

Each of these pockets is in communication with its own engaged tooth butnot with any other pocket or any other tooth. Consequently, while thesepockets are alternately under the suction and discharge pressure theycan notbe simultaneously under both, and as the liquid to be pumped isincompressible it swings freely around the pump.

As previously described the spuds 5 and. 7 are cylindrical in shape andthe latter is larger in diameter than the former. If the spud 7 weresuperimposed on Fig. 2 it would cover the area of 'a circle scribedabout the tips of the pinion teeth 15. If the spud '5 were superimposedon Fig. 2 it would cover the area of a circle scribed about the tips ofthe ring gear teeth 9. Due to their being disposed 'eccentrically thesespud circles would become tangent to each other at the bottom of thepinion where the pinion teeth 15 ride upon the crest of the ring gearvteeth 9, which is the'point of maximum disengagement.

The difference in the area of these spud circles would be a lunar shapedfigure starting at the point of common tangency and extendingtherearound, being thickest at the top of the pinion or at the full meshposition.

A portion of this differential of the areas of the spud faces plays animportant part in controlling the volume delivered by the rotating thepinion, which is fixed from axial-movement.

In-approaching this description from another view point the spuds 5 and7 may be looked upon as two differential stationary pistons dis-.- posedopposite to one another. The lower side of said pistons are tangent to acommon horizontal plane. The plate 26 and the rear'cylindrical end ofthe follower 22 may be looked upon as being movable cylinders which areassembled in one unit and are slidably operable longitudinally of thespuds 7 and 5 respectively. The cylinder (the plate 26) operating on thesmaller piston (the spud '7) will have a larger area exposed to theinternal pressure of the mechanism than does the other cylinder (therear end of the follower member 22) which differential area causes thecylinder unit to move to the left in Fig. 1 when-a pressure is developedwithin the pump. The rotating gears mounted within the cylinder unitbetween the differential cylinders seal, with the abutments 23 and 24,the

intake from the discharge side .of the mechanism and the actual usefuldifferential area of the pistons is the half lunar shaped area of thecylinder plate 26 exposed to the discharge pres-- sure of the pump. Thefunction of these differential 'spud faces will be enlarged upon after amore detailed discussion is had regarding some of the associated partsof the follower memben.

Attention is particularlydi'rected to the simplicity of thestructuralparts employed in my improved pump; In thisconnection it willbe noted that thepump includes but relatively few parts each of which inits manufacture ineludes or requires only simple machine operaions.

Essentially the pump includes but the casing.

or cylinder v1, the heads 4 and 6 carrying the spuds 5 and 7respectively, the pinion and the ring gear and the shaft for the pinion,and the follower structure. These parts, since they comprise for themost part only cylindrical surfaces, may obviously be completed 'orfinished by a simple-machine operation.

The follower may be manufactured without the use of complicated orexpensive machining operations and it and the plate 26 with the spud 5perform the added function of sealing or en-' closing those portions ofthe pinion and ring gear which at any time may be exposed due to ,thegears not being fully in mesh, as when the pump is set to.deliver lessthan its full volume.

For the most part the follower obviously comprises cylindrical surfaceswhich may be easily machined and the follower does not includeprojecting fingers or the like to seal or fill any exposed portions ofthe pinion or ring gear.

As in my prior patent, above referred to, in the present constructionvariations in volume being pumped are effected by varying the extent ofengagement of the teeth and the greater the degree of engagemenathegreater will be the pumping capacity of the device at constant speed. Inthe present construction, it will be seen that pressure inside the toothspaces between the gear and pinion on the discharge side of the pumpacts on the portionof the inner surface of the follower plate 26 whichrepresents the diiferential between the spud areas and tends to forcering gear 8 out of mesh with of discharge. This tendency of the followermember to slide the ring gear out of mesh with the pinion is checked andthe follower member is moved to vary'the capacity of the pump atconstant speed by cons ruction now to be de-- scribed.

As best shown iii-Figs. 5 and 6, a valve chamber 30 is formedwithinupper abutment 23 of follower member 22 .and is provided with ports 31,32, and 33. Port 31, through passage 34,

connects-the valve chamber with the discharge .oted by the link 41 tothe casing and having guide 42 fixed to the casing and upon which arm 40may be locked in any desired position by .the wing nut and bolt 43.

The enlargement 39 of the pilot valve fills the valve chambersubstantially pressure tight and in thenormal setting of the valve, theenlargement 39 is disposed directly opposite and just covering balancingport 32 which communicates with balancing chamber 28 through passage 35.

pinion 14 thereby tending to reduce the volume As best shown in Figure'5, pressure supply port 31, connected with the discharge side of thepump through passage 34, is disposed to the left of piston 39 whileexhaust port 33, communicating with the suction side of the pump, isdisposed to the right of piston 39.

In this normal setting of thepilot valve, it will be seen that anymovement of the follower to the left or toward head 4, caused by theinternal pressure in the pumping chamber working against the followerplate 26 by reason of the differential between the areas of the faces ofthe spuds, will cause port 32 to be slightly uncovered on the left ofpiston 39 thereby admitting pressure to balancing chamber 28 from thedischarge side of the pump or passage 12 through passage 34, port 31,partialh open port 32, and passage 35. It should be noted that the areaof the follower member 22 and the follower plate 26' exposed to thebalancing chamber 28 is considerably larger than the area exposed to theinternal pressure of the pump or the tooth spaces on the discharge sideof the pump, which area may be represented as onehalf of thedifferential between the spud areas as above explained. It is thusevident that the pressure required in the balancing chamber 28 tobalance the internal pressure of the pump need not be equal to theactual internal pressure of the pump because of the difference betweenthese two effective areas. In this way, the different pressures appliedon both sides of follower plate 26 may be made to balance and thefollower and ring gear maintained in any desired setting with respect tothe pinion since there is always more pressure available for use in thebalancing chamber than is necessary.

Assuming the pump to be in the substantially full volume position ofFigure 1, and it is desired to decrease the output of the pump or thevolume being pumped, pilot valve 36 is moved to the left or toward head4 by means of operat ing handle 40 so that piston 39 will be movedleftwise out of alignment with port 32 thereby establishingcommunication between balancing chamber 28 and suction passage 11through passage 35, port 32, valve chamber 30, and port 33. Thebalancing pressure within balancing chamber 28 will thus be dropped andthe follower member 22 will move forward in the direction of front head4 by reason of the internal pressure within the pumping chamber actingupon the pumping chamber side of the follower plate 26 and such forwardmovement of the follower member will continue until port 32 is againcovered by piston 39 whereupon communication between balancing chamber28 and suction passage 11 will be cut oil. and the follower will come torest at the new setting. Such movement of the follower member slidesring gear 8 laterally out of mesh with pinion 14 thereby decreasing thewidth of the engaging portions of the gear and pinion teeth andcorrespondingly decreasing the output of the pump.

'If it is desired to again increase the volume of liquid being pumped,pilot valve 36, is now moved rearward in the direction of rear head '6by means of the operating handle and port 32 uncovered on the left sideof piston 39. In this manner discharge passage 12 is placed incommunication with balancing chamber 28 through passage 34, port 31,valve chamber 30, port 32 and passage 35. Thus pressure isadmitted tobalancing chamber 28 from the discharge side of the pump through thepassages and ports just noted and this pressure will naturally build .bytouching at their tips.

up against the balancing chamber side of the follower plate 26 (which isof larger area than the area under pressure in the pumping chamber)until it overbalances the pressure within the pumping chamber on theopposite side of follower plate 26. The follower member 22 and gear 8'will thus be moved rearward toward head 6 until port 33 is againbrought in alignment with and closed by piston 39 thereby shutting offfurther supply of pressure from the discharge side of the pump tobalancing chamber 28. Such rearward movement of the follower member andring gear with respect to the pinion will increase the engaging portionsof the gear and pinion and thereby increase the volume of liquid beingpumped.

From the foregoing it will be seen that the follower will chase up.thepilot valve after each movement of the latter until the device comesback to the balanced position, that is, with the piston 39 closing port32 and the total pressures on both sides of plate 28 being substantiallyequal. In this way the follower and ring gear can be moved under loadwhen the pump is in operation without anyeffort and requires nomechanical locking in position except fixing the position of the pilotvalve.

To balance the pressure in chamber 29 at the rear of follower member 22,this chamber is simply connected to suction passage 11 by a balancingport 44 which permits oil or other liquid being pumped to,freely enteror leave chamber 29 as the volume of this chamber is increased ordecreased by movement of the follower. A relief port 45 is provided invalve chamber 30 behind front balancing piston 38, this port connectingwith suction passage 11 for releasing or admitting liquid from behindpiston 38 and also for completely balancing the valve 36 so that thereis no end thrust thereon.

For cooling and lubricating the bearings 20 and 21, spuds 5 and '1 areprovided respectively with passages 46 and 4'1 leading from the bearingsto the exterior of the casing and adapted to be connected back to thesuction side of the pump by means of pipes 50, as best shown in Figs. 2,'7 and 8. The arrangement illustrated takes all the pressure ofi theshaft packing 18 and also provides a definite pressure drop from thepump pressure spaces through the bearings which permits a flow of oilthrough the bearings back to the suction side of the pump. Oil flowsfrom the pumping chamber through bearings 20 and 21, passages 46 and 47,and pipes 50 back to the suction side of the pump, without exerting fullpressure on packing 18.

In the pump structure described and illus trated, it will be seen thatthe device is sealed against leakage without packing by reason of therelatively close clearances. Sealing between the ring gear and pinionteeth is accomplished in the usual manner of rotary gear type pump bythe pressure of the teeth upon each other. For all combinations ofexternal-internal gears of one tooth difference, it will be seen that ifthe tooth depth is twice the eccentricity, the teeth will seal at thedisengaged or bottom position The ring gear is sealed at its outerperiphery by the follower abutments 23 and 24, and the bearing surfaces25' and both the gear and pinion are sealed on their ends by contactwith spuds 5 and 7, follower member 22, and follower plate 26. Asdistinguished from the pump structure of my prior patent above referredto, it will be observed that in the present design there are at leasttwo line contacts on the teeth in series between the suction anddischarge sides, of the pump whereas in the construction of my priorpatent only one such contact'was maintained. Theleakage in the presentconstruction is therefore less than in that of my patent referred to.

Referring now to the constant volume motor or pump shown in Figs. 9 and10 wherein parts corresponding to elements of Figs. 1 to 8 aredesignated by corresponding primed reference numerals, 1? is the casingprovided at its upper portion with an inlet 2' and outlet 3 for theintroduction and discharge respectively of the liquid handled. The endsof the casing are closed by means of heads 4 and 6'. The internal orring gear 8' and pinion 14' aredisposed within the casing and adapted tobe rotated therein by means of shaft 17', but since there is nonecessity for variable volume, the

gears are not arranged to slide axially in or out of full mesh, but aremaintained constantly in full mesh. The follower and associatedmechanism for sliding one of the gears axially rela-. tive to the otherare therefore omitted, and the constructionsimplified to this extent.

End plates 26' are fastened within flanges or extensions 8 in the ringgear by snap rings 27' forming a closure for the tooth spaces 10 bycontact with the side faces of pinion '14. The extended flanges 8 may'be used as a journal bearing running in casing 1, or may serve, asshown in Fig. 8, as outer races for roller bearings 20, a form ofconstruction preferred when handling clean fluids. .The spuds and Iserve to support the inner races for the roller bearings 20, as well asthose for the pinion roller bearings 20. Suction passage 11 is sealedfrom discharge passage 12 by means of abutment 23' at the top andabutment 24' at the bottom,

,, these abutments being integral with the casing as shown.

When used. as a pump, the action is precisely the same as that for thevariable volume pump, except that since the gears are always in fullmesh, the volume discharged is constant for any given speed.

When used as a motonin conjunction with the variable volume pump, as ahydraulic variable speed transmission, the inlet 2 is supplied with"pressure liquid from the variable volume pump; the discharge3'. being atlow pressure, delivering liquid back to the suction of the variablevolume pump. Since the area of the teeth of the pinion and ring gearopposite the bottom abutment 24', where the gears are fully out of meshand exposed to the difierence of pressure between inlet and outlet, isgreater than that'opposite the top abutment 23', where the gears arefully in. mesh, by the area of one full tooth, a continuous torque isdeveloped that causes rotation of the gears. When used in combination,as a hydraulic transmission, the ratio of rotational speed of the motorto that of the variable volume pump is substantially inverselyproportional to the ratio of volume displacement of constant volumemotor per revolution, to that of the variable volume pump, at whatevermesh position axially the latter may be. i

As in the variable volume pump, passagesflfi and .47 are provided in theconstant volume pump or motor and these lead back to the suction side ofthe pumpso that oil may circulate through pinion roller bearings 20without exer ing full pressure on shaft packing 18'. Also as laterallyand very rapidly the full face With the radial ports 13 and 13' in thevariable volume pump, the lower abutment 24 spans a little more than onetooth space and two gear ports 13 while the upper abutment 23' is abouthalf the size of the lower abutment. The upper abutment is made smallerfor a purpose'hereinafter described. As" indicated by the arrows, thedirection of rotation in Fig. 10 is opposite that of Fig.2..

In most previous designs of rotary pump, especially gear forms,difllculty has developed due to trapping of liquid between the teeth atthe point of deepest engagement or full mesh due to inability to ventthe liquid fully therefrom. Unless such liquid is relieved up to the.point where the volume between the teeth becomes a minimum, extremelyheavy pressures aredeveloped between the gears, making it impossible toprevent damage to the bearings and gears. In rotary pumps consisting ofa pinion and internal gear differing by one or more teeth, but havingthe inlet and outlet ports opposite the lateral faces or sides of thegears, 'it has been found dimcult to eliminate such trapping completelyinasmuch as the liquid must travel width of the teeth in order toescape.

opening practically the entire width of the teeth, the. path for reliefof oil is short and itis possible to completely avoid trapping bysuitable placement of the entering edges 48 and 48'-of the top abutments23 and 23' respectively. For this purpose, it has been found desirableto set these entering edges 48 and 48' at least opposite the point ofdeepest engagement of the teeth where the volume between the pinion andring gear has become minimum. For very high speeds and viscous liquidssuch as oil, it is desirable to set the abutment edges 48 and 48' evenfurther forward in the direction of rotation by an amount not exceedingone-half the port width. The amount of such forward setting isdetermined by the rotational speed and the viscosity of the liquidpumped. By reference to Figs. 2 and 10, it will be seen that thearrangement of the sealing abutments 23 and .23 is. such that ports 13and 13 between the gear, teeth are in communication with the dischargepassages 12 and 12' respectively from the point of zero mesh at thebottom up to and including the point of maximum mesh at the top.Theports are pro.-

gressively closed by the upper sealing abutment as the gear rotatesaround the casing and it will be noted that the port of the tooth spacein full mesh with a pinion tooth is only partially closed by theabutment 23 or 23'. The port is fully closed by the upper abutment'onlyafter its corresponding tooth space has been in maximum or deepestengagement whereby, as already ex plained, the liquid is vented from thespace of minimum volume and. trapping avoided. By the time the port hasrotated around to the position of complete closure by abutment 23.0r23', its

corresponding tooth space has been relieved of preferred embodimentsherein chosen for illustration but that various changes andmodifications may be made therein without departing from the spirit andscope of the invention as hereinafter claimed.

Having thus described my invention, what I claim is:-

1. A rotary pump comprising a casing, an internal gear within saidcasing and forming suetion and discharge passages therewith, a pinionadapted to mesh with and having one tooth less than said gear,circumferentially spaced openings in said gear, a follower forming incombination with the casing and the gear a seal between said suction anddischarge passages and adapted to slide said gear relative to saidpinion, and means for moving said follower.

2. In a rotary pump, a pump casing having suction and dischargepassages, a movable follower member forming a seal between the sucitionand discharge passages and having a ring gear mounted for rotationtherein, a pinion adapted to mesh with and having one tooth less thansaid ring gear, a follower plate forming with said member a pumpingchamber enclosing said gear and pinion, and means for balancing pressureon opposite sides of said plate.

3. A rotary pump comprising a casing having a suction passage and adischarge passage, a slidable ring gear within said casing, a fixedpinion in mesh with and having one tooth less than said gear, a movablefollower member forming a seal between said suction and dischargepassages and adapted to slide said gear, circumferentially spaced portsin said gear, a follower plate fixed to said member and forming abalancing chamber with a wall of said casing, said plate also formingwith said member a pumping chamber enclosing said gear and pinion, andmeans in said member for alternately establishing communication betweensaid discharge passage and balancing chamber and between the latter andsaid suction passage.

4. A rotary pump comprising a casing, a movable follower member andplate forming a balancing chamber and a pumping chamber in said casing,a ring gear in said pumping chamber and movable with said followermember and plate, a fixed pinion meshing with and having one tooth lessthan said gear, means for supplying fluid to and discharging fluid fromsaid balancing chamber, and supply and discharge openings for saidpumping chamber.

5. A rotary pump comprising a casing, a movable follower member andplate forming a balancing chamber and a pumping chamber in said casing,a ring gear in said pumping chamber and movable with said followermember and plate, a fixed pinion meshing with and having one tooth lessthan said gear, suction and discharge passages communicating with saidpumping chamber, and means in said follower member for supplying fluidfrom said discharge passage to said balancing chamber and fordischarging fluid from said balancing chamber into said suction passage.

6. A rotary pump comprising a casing having a front head and spud and arear head and spud, a non-rotatable annular follower member slidableonsaid rear spud, an annular plate fixed to said follower member andslidable on said front spud, and forming one end of a pump chamber inthe follower, a ring gear mounted for rotation in said follower memberand slidable therewith, a fixed pinion between said spuds meshing withand having one tooth less than said gear, and means in said followermember for balancing pressure on opposite sides of said plate.

7. A rotary pump comprising a casing having a front head and spud and arear head and spud, a non-rotatable annular follower member slid- 'bleon said rear spud, an annular plate fixed to said follower member andslidable on said front spud, a ring gear mounted for rotation in saidfollower member and slidable therewith, a fixed pinion between saidspuds meshing with and having one tooth less than said gear, and meansfor moving said follower member.

8. A rotary pump comprising a casing having a front head and a spud anda rear head and spud, the spuds being disposed within the casing anddirected toward each other, a non-rotatable annular follower memberslidable on one of said spuds, an annular plate fixed to said followermember and slidable on the other of said spuds, a ring gear mounted forrotation in said member and slidable therewith, a fixed pinion betweensaid spuds meshing with said gear, means for moving said member to movesaid gear and thereby vary the engagement between the gear and pinion,said follower member being adapted to seal the portion of the pinion atany time out of mesh with the gear, and said other spud and said annularplate being adapted to seal the portion of the gear at any time out ofmesh with the pinion.

9. In a rotary pump, the combination of a pinion, an internal gear inengagement with said pinion, and adapted for sliding movement withrespect thereto, and means for sliding said gear to vary the extent ofmesh of the gear with said pinion, said means partially enclosing,entirely supporting and forming the bearing for said gear.

10. In a rotary pump, the combination of a pinion, an internal gear inengagement with and having one more tooth than said pinion, and meansmovable axially with respect to the easing and the pinion and forvarying the extent of the engagement between pinion and gear, said meanspartially enclosing, and entirely supporting said gear, and formingsuction and discharge ports.

11. A rotary pump comprising a casing, an annular follower slidableaxially therein, and forming suction and discharge passages therewith,an internal gear within said follower, means for sealing said suctionand discharge passages, openings in said gear between adjacent teeththereof, and a pinion adapted to mesh with and having one less tooththan said gear.

12. A rotary pump comprising a casing, an annular follower memberslidable longitudinally within said casing and forming a suction passageand a discharge passage therewith, an internal gear within said followermember and supported thereby, means for sealing said suction passagefrom said discharge passage, openings in said gear between adjacentteeth thereof, a pinion adapted to mesh with and having one tooth lessthan said gear, and means for sliding said follower to vary the extentof engagement between said gear and pinion.

13. In a rotary pump, the combination of a pinion, an internal gear inengagement therewith and having one tooth more than the pinion, afollower member movable axially of the pinion and partially enclosingand entirely supporting the gear and adapted to slide the gear '15. Arotary pump comprising a casing, a

movable follower member and plate forming a single balancing chamber anda pumping chamber in said casing, a ring gear in said pumping chambersupported by said follower member and movable with said follower memberand plate, a fixed pinion meshing with and having one tooth less thansaid gear, suction and discharge passages communicating with saidpumping chamber, a valve chamber in said follower member communicatingwith said suction and discharge passages and with said balancingchamber, and a valve movable in said valve chamber, movement of saidvalve relative to said follower member causing variation 'of fluidpressure in 'ripheral ports between.

said balancing chambensaid variation of fluid pressure causing saidfollower member to move in the same direction as said valve and with thesame amount of movement. v

16. In a liquid pump, a ring gear having peeach two consecutive teeth, apinion having one tooth less than the ring gear and operating therein, asuction chamber open to the ports on one side of the ring gear, adischarge chamber open to the ports on the opposite side of the ringgear, and an abutment arrangedto cut off each port as it passes out ofregistration with the suction chamber and to open said port as it passesinto registration with the discharge chamber, said abutment beingextended was to cut oii" the port. while the toothed space correspondingto the port and defined by consecutive teeth of the gear and pinion isexpanding and so as to open said port while said toothed space iscontracting.

1'7. In a liquid pump, a ring gear having peripheral .po'rts betweeneach two consecutive teeth, a pinion having cne tooth less than the ringgear and operating therein, a suction chamber open to the ports on oneside of the ring gear, a discharge chamber open to the ports on theopposite side of the ring gear, and an abutment sealing off the outerend of each port as it passes from .the discharge chamber, but onlyafter the pinion tooth cooperating with the port has'entered into itsfullest engagement with the ring gear teeth sealing oft the'inner end ofthe port, the seal being maintained continuously by the driving contactof the corresponding teeth of the pinion and the ring gear through thewhole distance through which the abutment seals the outer end of theport.

18. In a liquid pump, a ring gear having peripheral ports between. eachtwo consecutive teeth, a pinion having one tooth less than the ring gearand operating therein, a suction chamber open to the ports on one sideof the ring gear, a discharge chamber open tothe ports on the oppositeside of the ring gear, an

abutment arranged to cut off each port as it passes out of registrationwith the suction chamber and to open said port as it passes intoregistration with the discharge chamber, said abutment being extended soas to cut off the port while the toothed space corresponding to the portand defined by consecutive teeth of the gear and pinion is expanding andso as to open said port while said toothed space is contracting to avolume equal to or greater than that which it had at the point ofseal-off from the suction,

chamber, and an abutment sealing off the outer end of each port as itpasses from the discharge chamber, but only after the pinion toothcooperating with the port has entered into its fullest engagement withthe ring gear teeth sealing off the inner end of the port, the sealbeing maintained continuously by the driving contact of thecorresponding teeth of the pinion and the ring gear through the wholedistance, through which the abutment seals the outer end" of the port.

19. In a rotarypump having an inlet and an outlet, the combination of arotary pinion, an internal rotary gear to transfer liquid-from the inletto the outlet and arranged to mesh with and slide longitudinally of thepinion to vary the extent of engagement therebetween, a nonrotaryfollower member arranged to slide the gear and seal the portion of thepinion out of mesh with the gear, and means for moving the followermember.

20. In a rotary pump, the combination of a pair of rotors comprising aninternal gear having cireumferentially spaced suction and dischargeports in the periphery thereof and a pinion in mesh with said gear, anannular follower shiftable axially of the pinion and having opposedsurfaces of unequal eifective area, the lesser surface being exposed tothe discharge pressure of the pump, said gear being supported forrotation in said follower and arranged to be shifted therewith, andmeans whereby the pressure exerted against the follower surface oflarger area is varied to shift the follower and gear and thus regulatethe output capacity of the pump.

21..In a rotary pump, the combination with a casing having an inlet andan outlet, an internal gear in said casing and a pinion meshingtherewith, said gear and pinion being arranged to transfer fiuid fromthe inlet to the outlet of the pump, of a member mounted in said casingand arranged to slide axially .of the pinion, thegear being rotatablymounted on said member, said member having opposed surfaces of unequaleffective area, the lesser of V which is exposed to discharge pressureof said pump, and means comprising a valve and passages in said membercontrolled by said valve and arranged to shift said member by varying'the pump, of a member mounted in said casing and arranged to slideaxially of the pinion, the gear being rotatably supported by saidmember, said member having opposed surfaces of unequal effective area,the lesser of which is exposed to discharge pressure of said pump,passages in said member connecting the end of the casing wherein thepressure is effective against the surface of the member having largerefiective area to the outlet and to the inlet of the pump, a valve insaid.member arranged by movement relative to the member to selectivelyopen and close said passages, the valve member being so arranged thatwhen the valve has been adjusted to open one of said passages, theresulting pressure variation in said end of the casing will cause themember to shift and close the valve.

23. In a rotary pump, the combination with a casing having an inlet andan outlet, an internal gear element in said casing and a pinion elementmeshing therewith, said elements being arranged to transfer fluid fromthe inlet to the outlet, of a member mounted in said casing and arrangedto slide. in said casing, one of said elements being rotatably mountedon said member and arranged to slide therewith, said member havingopposed surfaces of unequal effective area, the lesser of which isexposed to the discharge pressure of the pump, and means comprising avalve and passages in said member controlled by said valve and arrangedto vary the pressure effective against the surface of larger area ofsaid member whereby to regulate the extent of engagement between saidelements.

24. In a rotary pump, the combination with a casing having an inlet andan outlet, an internal gear element in said casing and a pinion elementmeshing therewith, said elements being arranged to transfer fluid fromthe inlet to the outlet, of a member mounted in said casing and arrangedto slide in said casing, one of said elements being rotatably mounted onsaid member and arranged to slide therewith, said member having opposedsurfaces of unequal effective area, the lesser of which is exposed tothe discharge pressure of the pump, and means whereby the pressureeffective against the surface of larger area may be varied whereby tomove the member and thereby regulate the extent of engagement betweensaid elements.

25. In a rotary pump, the combination with a casing having an inlet andan outlet, an internal gear element in said casing and a pinion elementmeshing therewith, said elements being arranged to transfer fluid fromthe inlet to the outlet, of a member mounted in said casing and arrangedto slide in said casing, one of said elements being rotatably mounted onsaid member and arranged to slide therewith, said member having opposedsurfaces of unequal effective area, the lesser of which is exposed tothe discharge pressure of the pump, and means comprising a valve andpassages in said member controlled by said valve and arranged tomaintain the pressure effective against the surface of larger area ofsaid member for holding the gears in fixed relation.

26. A rotary pump comprising a casing having an inlet and an outlet, aninternal gear within said casing and having portions of its peripheryexposed to said inlet and outlet and arranged for both rotary and axialmovement, oppositely arranged spuds within the casing, one spud beinggreater in diameter than the other, a pinion rotatably mounted betweenthe spuds and arranged to mesh with said gear, and means actuated by thepressures generated within the pump for maintaining the extent of theengagement of the pinion and gear controlled by the difference betweenthe exposed areas of the spuds.

27. In a liquid pump, a ring gear having peripheral ports between eachtwo consecutive teeth, a pinion having one tooth less than the ring gearand operating therein, a suction chamber open to the ports on one sideof the ring gear for the greater portion of its semicircumferentialextent, a discharge chember open to the ports on the opposite side ofthe ring gear for the greater portion of its semicircumferential extent,and an abutment, arranged to cut off each port as it passes out ofregistration with the suction chamber and to open said port as it passesinto registration with the discharge chamber, said abutmentbeingextended so as to cut off the port while the toothed space correspondingto the port and defined by consecutive teeth of the gear and pinion isexpanding and so as to open said port while said toothed space iscontracting.

REGINALD J. S. PIGOTI

